The addi Click Hook set is intended as an upgrade or "booster pack" to the existing Click sets. Each travel pouch contains 8 Addi hooks: 3.75mm, 4.0mm (US F), 4.5mm (US G), 5.0mm (US H), 5.5mm (US I), 6.0mm (US J), 8.0mm (US L), and 9.0mm (US M). Each hook is 6.5" long, and can be used as a fixed hook (instead of attaching them to the Click cords). When combined with the Click cords and/or tips, the sets are perfect for double ended crochet, created Cro-Needles, Tunisian crochet (with the addition of the HeartStoppers - sold separately), and much, much more.